The present invention relates to displayed data scrolling and cursor position control in, e.g., a Japanese word processor and an electronic typewriter and, more particularly, to a display apparatus which can scroll displayed data with regard to a cursor position on a display screen.
Display apparatuses are often used to take advantage of visual observation of required information. A wordprocessor is one of various applications for the display apparatus. In a wordprocessor, a previously input document is read out and displayed on a screen, to allow correction to it. This, as well as a printing function, is an important function of the wordprocessor. However, it is difficult to display a one-page document (e.g., corresponding to A4-size paper) on a single screen because of hardware limitations and the like. For this reason, only a portion of the one-page document data is displayed on a screen, and is changed so as to display the entire page as needed. More specifically, the other portion of the one-page document data appears line by line when each line of the one-page document data displayed scrolls upward or downward.
In order to correct the document, a cursor is moved to a character to be corrected. In a conventional cursor control method, when a character to be corrected is not yet displayed, after a cursor for indicating a character position to be corrected is moved to an upper or lower end of the current screen, a cursor movement key is consecutively operated to scroll the screen. For example, the cursor is moved to a lower end of the screen by operating a cursor down-movement key, and when this key is further operated, a portion under the currently displayed portion of the document appears from the lower end of the screen by scrolling. The same scrolling occurs when a cursor up-movement key is operated after the cursor is moved to a top end of the screen. After a required document line has scrolled to a central portion of the screen upon successive operations of the cursor movement key, the cursor must be returned to the character position of interest. For this reason, in the conventional method, although displayed data is left unmoved and can be seen with ease, a cumbersome operation is required in practical use.
A means for eliminating the above problem is disclosed in West German (DE) Patent Application No. P2915673.8 and Japanese Patent Disclosure No. 55-140935. According to these disclosures, a cursor position is fixed at a given position on a screen even when a display movement key is operated or when characters are input, and only displayed data scrolls. In this method, however, since the screen scrolls continuously each time the movement key is operated, one cannot easily see the displayed data.
Accordingly, a display apparatus is desired, so that after desired data is displayed in the center region of the screen by scrolling, it can be fixed on the screen and the cursor can be moved elsewhere to input new data.